1. Field of the Invention
The present invention relates to a highly hydrophilic member precursor of many applications and to a hydrophilic member obtainable by utilization of said precursor. The invention also relates to a pattern forming material that utilizes the hydrophilic member and can easily form images of high resolution, to a support a highly hydrophilic surface for planographic printing plates, and to a planographic printing plate precursor capable of forming high-quality images with no stains in the non-image area thereof.
2. Description of the Related Art
Hydrophilicating various types of members on their surfaces endows them with many applications. Specific examples of such surface-hydrophilicated members include formed articles not almost absorbing proteins, colloids, bacteria, humins, oils and fats, and pollutants in air and other biocompatible shaped articles that are used in fields such as the food industry, medical treatment (including medical devices such as artificial organs, and for diagnosis), pharmaceutical industry, waste treatment, painting and printing; carriers for fixation not degrading enzymes and microbial cells; antifogging structures such as defrosting films and defrosting membranes to be used in the field of trading, agriculture, transportation, household appliances, optical instruments and coating compositions; and surface-hydrophilicated structures for static charge prevention usable in the field of electronic industry.
The surface characteristics necessary for those hydrophilic structures to be used in the various fields mentioned above are that their surfaces do not adsorb unfavorable substances such as proteins, oils, fats and humins; that they do not fog, they are biocompatible, and they are antistatic. High hydrophilicity realizes such their functions. For example, in the field of coating compositions, used are anti-soiling films that do not adsorb oily substances in rain; and especially for sensor surfaces, the coating compositions are required not to specifically adsorb such oily substances. When liquid drops adhere to antifogging films of high hydrophilicity, they may spread on the film surfaces and will widely wet the films. Therefore, such antifogging films are required not only to have high hydrophilicity but also to have high optical transparency and surface smoothness. Biocompatible articles for use in the field of medical treatment, for example, those for artificial organs are required to have surfaces not causing thrombosis, hemolysis, sensitization and antigen-antibody reaction. Structures that are hydrophilic and are therefore antistatic are especially important in the field of electronic industry.
Surface grafting with a hydrophilic monomer is one example of surface hydrophilication known in the art that satisfies these requirements.
Specifically, Japanese Patent Application Laid-Open (JP-A) No. 53-17407 discloses a method that comprises applying a hydrophilic radical-polymerizing compound to the surface of an oleophilic substrate of which the essential ingredient is an oleophilic resin having a predetermined amount of a hydrogen atom bonded to a carbon-carbon double bond and/or a tertiary carbon, followed by exposing the thus-coated substrate to active rays to thereby form a hydrophilic surface layer on the surface of the substrate. JP-A No. 10-53658 discloses a method for producing a shaped article having a hydrophilic surface, which comprises contacting (B) a hydrophilic layer-forming material that contains (b) a hydrophilic monomer and/or a hydrophilic oligomer with a photopolymerizing resin composition that contains indispensable ingredients of a monomer and/or an oligomer capable of polymerizing through exposure to active rays and a photopolymerization initiator, followed by exposing the thus-contacted two to active rays to thereby copolymerize the photopolymerizing resin composition (A) with the hydrophilic monomer and/or the hydrophilic oligomer in the hydrophilic layer-forming material (B) at the interface of the two.
In the method of producing surface-hydrophilic shaped articles disclosed by JP-A No. 53-17407, the hydrophilic surface layer is easy to form. However, the method is problematic in that that it is often difficult to uniformly coat the oleophilic substrate with such a hydrophilic radical-polymerizing compound of low film formability. Therefore, in the method, the substrate is often unevenly coated with the compound, and, as a result, the hydrophilicity of the hydrophilic surface layer formed on the substrate is often low. In the method disclosed by JP-A No. 10-53658, the support is exposed to light while dipped in a hydrophilic layer-forming material to thereby form a hydrophilic layer thereon. Therefore, the method is disadvantageous in point of the process latitude. In particular, when a shaped article of a filmy substrate coated with a hydrophilic layer is produced according to the method, the surface smoothness of the article produced is often poor.
Heretofore, various image-forming materials are used for display materials and pattern forming materials. In general, images are formed in these materials by imagewise adhering a colorant material such as ink to the surface of a white image-receiving material such as paper, or by imagewise adhering a light-impervious material such as pigment to a transparent image-receiving material such as plastic film.
Various methods of image formation are known, for example, comprising adhering ink to an image-receiving material in a mode of inkjet printing, or comprising electrostatically adhering a colorant to the surface of an image-forming material followed by heating it for image fixation thereon, typically as in copiers, or comprising imagewise coloring a dye precursor in a thermal recording material.
For forming fine patterns of controlled orientation, for example, JP-A No. 2000-247799 proposes a method of forming a thin film of functional organic molecules. The method produces fine patterns, in which, however, the image-forming material must be exposed to UV rays through a mask such as a lith film for writing imagewise patterns thereon, like in a method of image formation on conventional planographic printing plate precursors. Therefore, the method requires complicated steps for image formation.
In ordinary image-forming methods heretofore known in the art, it is difficult to form images of high resolution on large-area image-forming materials and to form images of high density on thin-film image-forming materials.
A printing plate having an ink-receiving oleophilic region and an ink-repellent region (hydrophilic resin) to receive not ink but dampening water is used in lithography, and various types of photosensitive planographic printing plate precursors (PS precursors) are used for it.
One type of PS precursors now widely used in practice has a photosensitive layer formed on a support such as an aluminium plate. The PS precursor of the type is imagewise exposed and developed to remove the photosensitive layer in the non-image area, and the thus-processed plate is used in printing, based on the hydrophilicity of the substrate surface and the hydrophobicity of the photosensitive layer in the image area. The substrate surface of the PS precursor must be highly hydrophilic for preventing the non-image area thereof from being stained.
For the hydrophilic substrate or the hydrophilic layer of planographic printing plates, heretofore generally used are aluminium plates having been subjected to anodic oxidation to form an oxide film thereon, or the oxide film-coated aluminium plates are silicated for further increasing their hydrophilicity. Many studies relating to such hydrophilicated substrates of aluminium supports and to such hydrophilic layers formed on aluminium substrates are made these days. For example, JP-A No. 7-1853 discloses a substrate processed with an undercoating agent of polyvinylphosphonic acid; and JP-A 59-101651 discloses a technique of using a sulfonic acid group-having polymer for the undercoat layer to underlie a photosensitive layer. In addition, also proposed is a technique of using polyvinylbenzoic acid for the undercoating agent for supports.
On the other hand, flexible supports of, for example, PET (polyethylene terephthalate) or cellulose triacetate may be used in place of metal supports of aluminium, and various techniques relating to hydrophilic layers for are proposed. For example, JP-A No. 8-292558 discloses a swellable hydrophilic layer comprising a hydrophilic polymer and a hydrophobic polymer; EP 0709228 discloses a PET support having a microporous, hydrophilic crosslinked silicate surface; and JP-A Nos. 8-272087 and 8-507727 disclose a hydrophilic layer containing a hydrophilic polymer and cured with a hydrolyzed tetraalkyl orthosilicate.
These hydrophilic layers are more hydrophilic than conventional ones, and give planographic printing plates that produce good prints with no stain at the start of printing with them. However, they are problematic in that they often peel off and their hydrophilicity lowers while used repeatedly in printing. At present, therefore, it is desired to obtain planographic printing plates in which the hydrophilic layer does not peel off from the support and the hydrophilicity of the support surface does not lower even in severer printing conditions and which can therefore produce a large number of good prints with no stain. In addition, it is also desired to further increase the hydrophilicity of the support surface of planographic printing plates from the practical viewpoint in printing, and supports for planographic printing plates that are highly hydrophilic and durable to satisfy the requirements are desired.
On the other hand, recently, a method of forming images on an image-forming material directly from digitalized image data not via any medium such as lith film has been specifically noticed in the art.
Various studies relating to such printing plates for computer-to-plate systems are now made. For solving the problem of further process rationalization and waste treatment in such systems, for example, development-less planographic printing plate precursors capable of being directly set in printers not requiring development after exposure for image formation thereon are studied, and various methods for them have been proposed.
One method not requiring development comprises directly setting an exposed planographic printing plate precursor on the cylinder of a printer followed by applying dampening water and ink thereto with rotating the cylinder to thereby remove the non-image area of the printing plate precursor. This is referred to as in-printer development. According to this, a printing plate precursor is, after exposed, directly set in a printer and processed therein into a printing plate in an ordinary printing process.
The planographic printing plate precursor suitable to such in-printer development shall have a photosensitive layer soluble in dampening water or ink solvents, and it must be handlable even in light in order that it can be processed in printers put in light rooms.
For example, Japanese Patent 2,938,397 discloses a planographic printing plate precursor having, on a hydrophilic support, a thermal recording layer that contains fine particles of a thermoplastic hydrophobic polymer dispersed in a hydrophilic binder. This says that the planographic printing plate precursor disclosed accepts in-printer development. Specifically, the planographic printing plate precursor is exposed to IR laser to thereby thermally fuse the fine particles of the thermoplastic hydrophobic polymer for image formation thereon, and the thus-processed printing plate precursor is set on the cylinder of a printer and developed thereon with dampening water and/or ink applied thereto in the printer.
In the method of image formation through thermal fusion of polymer particles, the non-image region of the recoding layer enjoys good in-printer development. However, the method is problematic in that the mechanical strength of the image region of the recording layer is low and therefore the printing service durability of the printing plate is insufficient. In addition, in case where the thermal recording layer is directly formed on an aluminium substrate that is popular in planographic printing plate precursors, the heat generated in exposure is much taken by the aluminium substrate of high thermal conductivity and, as a result, the thermal energy could not be fully used for image formation, or that is, for thermal fusion of the fine polymer particles around the interface between the substrate and the thermal recording layer. If so, the image region could not be well cured, and the printing service durability of the printing plate is insufficient. This is another problem with the method.